After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa ar...After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa are investigated.It is found that as the aging time increases from 0 to 5000 h,the average diameter of coarseγ′increases from 241 to 484 nm,and the distribution of the carbides at grain boundaries changes from discontinuous to continuous.Moreover,experimental observations on the microstructures of all the crept specimens reveal that dislocation bypassing controls the creep deformation.Thus,it is concluded that the transitions in the microstructures result in the degeneration of the creep rupture properties of the experimental alloy with aging time.展开更多
A numerical study of the crushing of thin-walled circular aluminum tubes has been carried out to investigate the crashworthiness behaviors under axial impact loading. These kinds of tubes are usually used in automobil...A numerical study of the crushing of thin-walled circular aluminum tubes has been carried out to investigate the crashworthiness behaviors under axial impact loading. These kinds of tubes are usually used in automobile and train structures to absorb the impact energy. Previous researches show that thin-walled circular tube has the highest energy absorption under axial impact amongst different structures. In this work, the crushing between two rigid flat plates and the tube rupture by 4 and 6 blades cutting tools is modeled with the help of ductile failure criterion using the numerical method. The tube material is aluminum EN AW-7108 T6 and its length and diameter are 300 mm and 50 ram, respectively. Using the artificial neural network （ANN）, the most important surfaces of energy absorption parameters, including the maximum displacement of the striker, the maximum axial force, the specific energy absorption and the crushing force efficiency in terms of impact velocity and tube thickness are obtained and compared to each other. The analyses show that the tube rupture by the 6 blades cutting tool has more energy absorption in comparison with others. Furthermore, the results demonstrate that tube cutting with the help of multi-blades cutting tools is more stable, controllable and predictable than tube folding.展开更多
Three experimental single crystal superalloys with 0%Nb,0.5%Nb,1.0%Nb were cast in the directionally solidified furnace,while other alloying element contents were basically kept unchanged.The effect of Nb on the micro...Three experimental single crystal superalloys with 0%Nb,0.5%Nb,1.0%Nb were cast in the directionally solidified furnace,while other alloying element contents were basically kept unchanged.The effect of Nb on the microstructure,stability at1100°C and stress rupture properties at 1070°C and 160 MPa of the single crystal superalloy were investigated.The experiment results show that the primary dendrite arm spacing decreases and the volume fraction ofγ/γ′eutectic of the alloy increases with the increase of Nb content in the as-cast microstructures.The size ofγ′phase particles becomes small and uniform and the cubic shape does not obviously change with the increase of Nb content.The precipitating rate and volume fraction of TCP phases increase significantly with the increase of Nb content in the process of long term aging at 1100°C.The stress rupture lives increase and elongation decreases with increasing Nb content at 1070°C/160 MPa.At last,the relationship between the microstructures stability,stress rupture properties of the alloy and Nb content is discussed based on JMat Pro software and the lastest relevant database for single crystal superalloy.展开更多
Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become ex...Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become extremely important for patient risk stratification.Previous studies have shown that the vulnerable plaque,i.e.one that is prone to rupture with thromboembolic complications,is often associated with a thin fibrous cap,a large lipid core and a high inflammatory burden.The mechanism of plaque rupture is not entirely clear but is thought to be a multi-factorial process involving thinning and weakening of the fibrous cap by enzymes secreted by activa-展开更多
子宫肌瘤是育龄期女性常见多发疾病,腹腔镜子宫肌瘤剔除术是目前临床最常用的治疗方法。子宫肌瘤剔除术后妊娠期子宫破裂(uterine rupture during pregnancy,URDP)是最严重的远期并发症,可能会造成灾难性的后果,必须引起临床医生的足够...子宫肌瘤是育龄期女性常见多发疾病,腹腔镜子宫肌瘤剔除术是目前临床最常用的治疗方法。子宫肌瘤剔除术后妊娠期子宫破裂(uterine rupture during pregnancy,URDP)是最严重的远期并发症,可能会造成灾难性的后果,必须引起临床医生的足够重视。本文对腹腔镜子宫肌瘤剔除术后URDP的预后因素进行文献总结,为妇科医生手术提供临床依据,提高手术技巧,将URDP的风险降到最低。展开更多
未足月胎膜早破(preterm prelabour rupture of membranes,PPROM)的定义为临产前胎膜自发破裂,且发生于妊娠37周前。PPROM的发生率约为3%,在所有早产的病因中约占三分之一。在加拿大,早产的发生率为8%,在过去10年中增长了近25%。尽管PP...未足月胎膜早破(preterm prelabour rupture of membranes,PPROM)的定义为临产前胎膜自发破裂,且发生于妊娠37周前。PPROM的发生率约为3%,在所有早产的病因中约占三分之一。在加拿大,早产的发生率为8%,在过去10年中增长了近25%。尽管PPROM后早产的发生率较高,但PPROM的最佳管理仍是一个有争议的话题,这受限于证据不足。展开更多
Directional rupture is one of the difficult problems in deep rock mechanics and engineering.A directional fracturing method with static expansive agent controlled by dense linear multi boreholes is proposed.A physical...Directional rupture is one of the difficult problems in deep rock mechanics and engineering.A directional fracturing method with static expansive agent controlled by dense linear multi boreholes is proposed.A physical experiment is designed and performed to investigate the basic laws of this method.The fracture initiation and propagation process,and the mechanism of directional fracturing are analyzed.The results indicate that a directional fracture is formed along the direction of boreholes layout through directionally fracturing with static expansive agents controlled by the dense linear multi boreholes.According to the variation of strain and the distribution of associated acoustic emission(AE)events and energy,the experiment can be divided into three stages.In the first stage,the static expansive agent expand slowly with no fracturing inside the rock.In the second stage,some initial micro-fracturing occurs inside the rock.In the third stage,a wide range of fracturing occurs inside the sample.The internal micro-fracturing planes are connected to form a macro-fracture.Finally,it propagates to the surface of the sample.The directional fracturing plane presents a relatively smooth plane with little bias but much local fluctuation.展开更多
According to trends of the development the high-voltage devices’ usage and unpredictable weather causes,we find it very important to research electrical discharge from different sources.In our opinion,the most import...According to trends of the development the high-voltage devices’ usage and unpredictable weather causes,we find it very important to research electrical discharge from different sources.In our opinion,the most important is to analyze an influence of the atmospheric electricity on the air and ground, create an exact mathematical model of the physical processes,and describe the ecological influence.展开更多
Forced dissociation of selectin-ligand complex is crucial to such biological processes as leukocyte recruitment,thrombosis formation,as well as tumor metastasis<sup>[</sup>1].Although several assays and te...Forced dissociation of selectin-ligand complex is crucial to such biological processes as leukocyte recruitment,thrombosis formation,as well as tumor metastasis<sup>[</sup>1].Although several assays and techniques,e.g.,dynamic force spectroscopy（DFS）,have been applied to probe the complex at single-bond level,the discrepancies in the loading rate dependence of bond rupture force were found in the assays,presumably due to the different pathways in energy landscape and binding kinetics of molecular complexes<sup>[2]</sup>.However,the underlying mechanisms remain unclear.Here an optical trap（OT）assay was used to quantify the bond rupture at r<sub>f</sub>≤20 pN/s展开更多
In land warfare,trenches serve as vital defensive fortifications,offering protection to soldiers while engaging in combat.However,despite their protective function,soldiers often sustain injuries within these trenches...In land warfare,trenches serve as vital defensive fortifications,offering protection to soldiers while engaging in combat.However,despite their protective function,soldiers often sustain injuries within these trenches.The lack of corresponding blast data alongside empirical injury reports presents a significant knowledge gap,particularly concerning the blast pressures propagating within trench spaces following nearby explosions.This absence hinders the correlation between blast parameters,trench geometry,and reported injury cases,limiting our understanding of blast-related risks within trenches.This paper addresses the critical aspect of blast propagation within trench systems,essential for evaluating potential blast injury risks to individuals within these structures.Through advanced computational fluid dynamics(CFD)simulations,the study comprehensively investigates blast injury risks resulting from explosions near military trenches.Employing a sophisticated computational model,the research analyzes the dynamic blast effects within trenches,considering both geometrical parameters and blast characteristics influenced by explosive weight and scaled distance.The numerical simulations yield valuable insights into the impact of these parameters on blast injury risks,particularly focusing on eardrum rupture,lung injury,and traumatic brain injury levels within the trench.The findings elucidate distinct patterns of high-risk zones,highlighting unique characteristics of internal explosions due to confinement and venting dynamics along the trench.This study underscores the significance of detailed numerical modeling in assessing blast injury risks and provides a novel knowledge base for understanding risks associated with explosives detonating near military trenches.The insights gained contribute to enhancing safety measures in both military and civilian contexts exposed to blast events near trench structures.展开更多
Morocco and Algeria decided on May 16 to re-establish diplomatic relations ruptured 12 years ago. Memorial services on May 18 for the victims of a 1980 student revolt in Kwangju, South Korea, sparked vehement antigove...Morocco and Algeria decided on May 16 to re-establish diplomatic relations ruptured 12 years ago. Memorial services on May 18 for the victims of a 1980 student revolt in Kwangju, South Korea, sparked vehement antigovernment actions. On May 23, South Korean students shouting anti-American slogans展开更多
基金Project(2018BSHQYXMZZ32)supported by the Postdoctoral Science Foundation of Shaanxi Province of ChinaProject(20192109)supported by the State Key Laboratory for Mechanical Behavior of Materials,ChinaProjects(2017M623213,2018M633487)supported by the Postdoctoral Science Foundation of China
文摘After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa are investigated.It is found that as the aging time increases from 0 to 5000 h,the average diameter of coarseγ′increases from 241 to 484 nm,and the distribution of the carbides at grain boundaries changes from discontinuous to continuous.Moreover,experimental observations on the microstructures of all the crept specimens reveal that dislocation bypassing controls the creep deformation.Thus,it is concluded that the transitions in the microstructures result in the degeneration of the creep rupture properties of the experimental alloy with aging time.
文摘A numerical study of the crushing of thin-walled circular aluminum tubes has been carried out to investigate the crashworthiness behaviors under axial impact loading. These kinds of tubes are usually used in automobile and train structures to absorb the impact energy. Previous researches show that thin-walled circular tube has the highest energy absorption under axial impact amongst different structures. In this work, the crushing between two rigid flat plates and the tube rupture by 4 and 6 blades cutting tools is modeled with the help of ductile failure criterion using the numerical method. The tube material is aluminum EN AW-7108 T6 and its length and diameter are 300 mm and 50 ram, respectively. Using the artificial neural network （ANN）, the most important surfaces of energy absorption parameters, including the maximum displacement of the striker, the maximum axial force, the specific energy absorption and the crushing force efficiency in terms of impact velocity and tube thickness are obtained and compared to each other. The analyses show that the tube rupture by the 6 blades cutting tool has more energy absorption in comparison with others. Furthermore, the results demonstrate that tube cutting with the help of multi-blades cutting tools is more stable, controllable and predictable than tube folding.
文摘Three experimental single crystal superalloys with 0%Nb,0.5%Nb,1.0%Nb were cast in the directionally solidified furnace,while other alloying element contents were basically kept unchanged.The effect of Nb on the microstructure,stability at1100°C and stress rupture properties at 1070°C and 160 MPa of the single crystal superalloy were investigated.The experiment results show that the primary dendrite arm spacing decreases and the volume fraction ofγ/γ′eutectic of the alloy increases with the increase of Nb content in the as-cast microstructures.The size ofγ′phase particles becomes small and uniform and the cubic shape does not obviously change with the increase of Nb content.The precipitating rate and volume fraction of TCP phases increase significantly with the increase of Nb content in the process of long term aging at 1100°C.The stress rupture lives increase and elongation decreases with increasing Nb content at 1070°C/160 MPa.At last,the relationship between the microstructures stability,stress rupture properties of the alloy and Nb content is discussed based on JMat Pro software and the lastest relevant database for single crystal superalloy.
基金partially supported by the National 973 Basic Research Program of China (No.2013CB733803)the National Natural Science Foundation of China(NSFC)(No.11272091)
文摘Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become extremely important for patient risk stratification.Previous studies have shown that the vulnerable plaque,i.e.one that is prone to rupture with thromboembolic complications,is often associated with a thin fibrous cap,a large lipid core and a high inflammatory burden.The mechanism of plaque rupture is not entirely clear but is thought to be a multi-factorial process involving thinning and weakening of the fibrous cap by enzymes secreted by activa-
文摘子宫肌瘤是育龄期女性常见多发疾病,腹腔镜子宫肌瘤剔除术是目前临床最常用的治疗方法。子宫肌瘤剔除术后妊娠期子宫破裂(uterine rupture during pregnancy,URDP)是最严重的远期并发症,可能会造成灾难性的后果,必须引起临床医生的足够重视。本文对腹腔镜子宫肌瘤剔除术后URDP的预后因素进行文献总结,为妇科医生手术提供临床依据,提高手术技巧,将URDP的风险降到最低。
文摘未足月胎膜早破(preterm prelabour rupture of membranes,PPROM)的定义为临产前胎膜自发破裂,且发生于妊娠37周前。PPROM的发生率约为3%,在所有早产的病因中约占三分之一。在加拿大,早产的发生率为8%,在过去10年中增长了近25%。尽管PPROM后早产的发生率较高,但PPROM的最佳管理仍是一个有争议的话题,这受限于证据不足。
基金Project(2017YFC0603001)supported by the National Key Research and Development Program of ChinaProjects(51774272,52004269)supported by the National Natural Science Foundation of ChinaProject(2019M661995)supported by the China Postdoctoral Sciences Foundation。
文摘Directional rupture is one of the difficult problems in deep rock mechanics and engineering.A directional fracturing method with static expansive agent controlled by dense linear multi boreholes is proposed.A physical experiment is designed and performed to investigate the basic laws of this method.The fracture initiation and propagation process,and the mechanism of directional fracturing are analyzed.The results indicate that a directional fracture is formed along the direction of boreholes layout through directionally fracturing with static expansive agents controlled by the dense linear multi boreholes.According to the variation of strain and the distribution of associated acoustic emission(AE)events and energy,the experiment can be divided into three stages.In the first stage,the static expansive agent expand slowly with no fracturing inside the rock.In the second stage,some initial micro-fracturing occurs inside the rock.In the third stage,a wide range of fracturing occurs inside the sample.The internal micro-fracturing planes are connected to form a macro-fracture.Finally,it propagates to the surface of the sample.The directional fracturing plane presents a relatively smooth plane with little bias but much local fluctuation.
文摘According to trends of the development the high-voltage devices’ usage and unpredictable weather causes,we find it very important to research electrical discharge from different sources.In our opinion,the most important is to analyze an influence of the atmospheric electricity on the air and ground, create an exact mathematical model of the physical processes,and describe the ecological influence.
基金supported by National Natural Science Foundation of China grants 10902117, 31230027,30730032,and 10332060
文摘Forced dissociation of selectin-ligand complex is crucial to such biological processes as leukocyte recruitment,thrombosis formation,as well as tumor metastasis<sup>[</sup>1].Although several assays and techniques,e.g.,dynamic force spectroscopy（DFS）,have been applied to probe the complex at single-bond level,the discrepancies in the loading rate dependence of bond rupture force were found in the assays,presumably due to the different pathways in energy landscape and binding kinetics of molecular complexes<sup>[2]</sup>.However,the underlying mechanisms remain unclear.Here an optical trap（OT）assay was used to quantify the bond rupture at r<sub>f</sub>≤20 pN/s
文摘In land warfare,trenches serve as vital defensive fortifications,offering protection to soldiers while engaging in combat.However,despite their protective function,soldiers often sustain injuries within these trenches.The lack of corresponding blast data alongside empirical injury reports presents a significant knowledge gap,particularly concerning the blast pressures propagating within trench spaces following nearby explosions.This absence hinders the correlation between blast parameters,trench geometry,and reported injury cases,limiting our understanding of blast-related risks within trenches.This paper addresses the critical aspect of blast propagation within trench systems,essential for evaluating potential blast injury risks to individuals within these structures.Through advanced computational fluid dynamics(CFD)simulations,the study comprehensively investigates blast injury risks resulting from explosions near military trenches.Employing a sophisticated computational model,the research analyzes the dynamic blast effects within trenches,considering both geometrical parameters and blast characteristics influenced by explosive weight and scaled distance.The numerical simulations yield valuable insights into the impact of these parameters on blast injury risks,particularly focusing on eardrum rupture,lung injury,and traumatic brain injury levels within the trench.The findings elucidate distinct patterns of high-risk zones,highlighting unique characteristics of internal explosions due to confinement and venting dynamics along the trench.This study underscores the significance of detailed numerical modeling in assessing blast injury risks and provides a novel knowledge base for understanding risks associated with explosives detonating near military trenches.The insights gained contribute to enhancing safety measures in both military and civilian contexts exposed to blast events near trench structures.
文摘Morocco and Algeria decided on May 16 to re-establish diplomatic relations ruptured 12 years ago. Memorial services on May 18 for the victims of a 1980 student revolt in Kwangju, South Korea, sparked vehement antigovernment actions. On May 23, South Korean students shouting anti-American slogans
